<template>
    <el-select :value="valueTitle" :clearable="clearable" @clear="clearHandle" class="w-full">
        <el-option :value="valueTitle" :label="valueTitle" class="options">
            <el-tree
                    v-if="lazy"
                    class="tree-option"
                    ref="selectTree"
                    :accordion="accordion"
                    lazy
                    :load="loadNode"
                    :props="props"
                    :node-key="props.value"
                    :default-expanded-keys="defaultExpandedKey"
                    @node-click="handleNodeClick">
            </el-tree>
            <el-tree
                    v-else
                    class="tree-option"
                    ref="selectTree"
                    :accordion="accordion"
                    :data="options"
                    :props="props"
                    :node-key="props.value"
                    :default-expanded-keys="defaultExpandedKey"
                    @node-click="handleNodeClick">
            </el-tree>
        </el-option>
    </el-select>
</template>

<script>
    export default {
        name: "el-tree-select",
        props: {

            // 配置项
            props: {
                type: Object,
                default: {
                    value: 'id',             // ID字段名
                    label: 'title',         // 显示名称
                    children: 'children'    // 子级字段名
                }
            },

            // 选项列表数据(树形结构的对象数组)
            options: {type: [Array, null]},

            // 初始值
            value: {type: [Number, String], default: null},

            // 可清空选项
            clearable: {type: Boolean, default: true},

            // 自动收起
            accordion: {type: Boolean, default: true},

            lazy: {type: Boolean, default: false},

        },
        data() {
            return {
                valueId: null,
                valueTitle: '',
                defaultExpandedKey: []
            }
        },
        mounted() {
            if(!this.lazy){
                this.valueId = this.value    // 初始值
                this.initHandle()
            }
        },
        methods: {
            // 初始化值
            initHandle() {
                if (this.valueId) {
                    this.$nextTick(()=>{
                        this.valueTitle = this.$refs.selectTree.getNode(this.valueId).data[this.props.label]     // 初始化显示
                        this.$refs.selectTree.setCurrentKey(this.valueId)       // 设置默认选中
                        this.defaultExpandedKey = [this.valueId]      // 设置默认展开
                    })
                }
                //this.initScroll()
            },

            // 初始化滚动条
            initScroll() {
                this.$nextTick(() => {
                    let scrollWrap = document.querySelectorAll('.el-scrollbar .el-select-dropdown__wrap')[0]
                    let scrollBar = document.querySelectorAll('.el-scrollbar .el-scrollbar__bar')
                    scrollWrap.style.cssText = 'margin: 0px; max-height: none; overflow: hidden;'
                    scrollBar.forEach(ele => ele.style.width = 0)
                })
            },

            // 切换选项
            handleNodeClick(node) {
                this.valueTitle = node[this.props.label]
                this.valueId = node[this.props.value]
                this.$emit('getValue', this.valueId)
                this.defaultExpandedKey = []
            },

            // 清除选中
            clearHandle() {
                this.valueTitle = ''
                this.valueId = null
                this.defaultExpandedKey = []
                this.clearSelected()
                this.$emit('getValue', null)
            },

            // 清空选中样式
            clearSelected() {
                let allNode = document.querySelectorAll('.tree-option .el-tree-node')
                allNode.forEach((element) => element.classList.remove('is-current'))
            },
            loadNode(node, resolve) {
                this.$emit('loadNode', node, resolve)
            },

        },

        watch: {
            value() {
                if (!this.lazy) {
                    this.valueId = this.value
                    this.initHandle()
                }
            }
        },
    }
</script>

<style scoped>
    .el-scrollbar .el-scrollbar__view .el-select-dropdown__item {
        height: auto;
        padding: 0;
        /*max-height: 274px;
        overflow: hidden;
        overflow-y: auto;*/
    }

    .el-select-dropdown__item.selected {
        font-weight: normal;
    }

    ul li >>> .el-tree .el-tree-node__content {
        height: auto;
        padding: 0 20px;
    }

    .el-tree-node__label {
        font-weight: normal;
    }

    .el-tree >>> .is-current .el-tree-node__label {
        color: #409EFF;
        font-weight: 700;
    }

    .el-tree >>> .is-current .el-tree-node__children .el-tree-node__label {
        color: #606266;
        font-weight: normal;
    }
</style>
